3.5 Scope of Problems

3.5 Scope of Problems

By the time a report has been generated from a data warehouse, there
have been a lot of opportunities for the data to go wrong. The errors just
accumulate from initial data creation through decay, data movement, and use. No
wonder so many data decision support systems are judged failures.

Some practitioners take comfort in believing that data accuracy
problems are greater in legacy systems than they are in systems built more
recently, systems on a relational base, or systems implemented through a
packaged application. The truth is that there are many opportunities to create
problems in all of these.

Relational systems are not immune to errors. This is particularly
true of relational systems built in the 1980s. Much of the current protection
capability of relational systems was introduced gradually throughout the 1980s.
This included date/time data types, triggers, procedures, and referential
constraints. Many of the older systems do not use these capabilities and thus
leave themselves open to inaccurate data.

Packaged applications do not protect against bad data. They provide a
framework for collecting and storing data, but only the using company generates
and is responsible for the data. The packaged application cannot ensure that
all data is collected, that all values are accurate, or that the fields are
being used as intended. Using companies often make local customization
decisions in order to force the packaged application to fit their way of doing
business. This can lead to problems in extracting, moving, and interpreting
data.